


part of your world

by prodbeomgyu



Category: TOMORROW X TOGETHER | TXT (Korea Band)
Genre: Alternate Universe - The Little Mermaid Fusion, Fluff, Light Angst, M/M, Mermaid kang taehyun, Prince Huening Kai, Sea Sorcerer Choi Yeonjun, Siren Kang Taehyun, beomjun if you squint, but he thinks siren sounds cooler, i somehow manage to fit beomjun into everything
Language: English
Status: Completed
Published: 2020-10-31
Updated: 2020-10-31
Packaged: 2021-03-08 19:27:43
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,570
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27291940
Author URL: https://archiveofourown.org/users/prodbeomgyu/pseuds/prodbeomgyu
Summary: Having been under the sea his whole life, Taehyun meets a human and discovers for the first time how it feels to drown.
Relationships: Huening Kai/Kang Taehyun
Comments: 16
Kudos: 105





	part of your world

**Author's Note:**

> commission for anri. (thank you again <3)
> 
> unbeta-ed.

It must be so nice, Taehyun thinks, it must be so nice to be above. 

He doesn’t necessarily hate the sea, it’s vast and it’s home—it will always provide him with the comfort that even exploring dry land for once won’t be able to give him. It has its own treasures and mysteries too; Taehyun is aware that there are crevices within the sea that humankind can only wish to touch. 

But besides the fact that he has spent almost two decades wandering aimlessly under the surface and is almost bored with already having seen most of what the sea has to offer, there have been admittedly a few times where in Taehyun swam upwards in secret and witnessed humans on ships that have left him awestruck and fascinated.

Life on land, life with humans. He can’t help but daydream about it. If he were up there with people, would he be able to do the same as them? 

Each trip back above water, Taehyun swims closer and closer to the shore, unable to keep his curiosity and wonder at bay. 

He makes sure to keep distance when ships pass by and dives back down to ensure no human catches sight of him. The siren isn’t naive enough to believe that the beings on the surface have no intention of harming creatures below, he has heard multiple stories from friends and relatives that there are people seeking to capture them for profit and fame. 

It’s dreadful, sure. But still. 

Taehyun knows it’s impossible for him to even spend a day on the sand, so he at least deserves to see glimpses of it—of the clouds scattered across the blue cosmos, of the big ball of light shedding warmth on everything it can reach. 

Of the peculiar boy alone on the shore. 

Taehyun first saw him when he mustered enough courage, and perhaps recklessness, to move as close as he could to land. He swam closer until he could see the island’s large trees and wooden huts, without going beyond the boulder big enough for him to hide behind. 

The boy was performing unfamiliar movements, randomly moving his  _ feet? _ and arms. They were foreign to the siren’s eyes, yet intriguing. Each sway of the boy’s arm and each step of his foot only intensified the odd, magnetizing pull Taehyun felt. 

Humans are strange, he said to himself that afternoon. 

He continues to come back to the same shore in hopes of seeing the boy doing the weird movements again. Sometimes he does, sometimes he doesn’t, sometimes he catches the boy only to see him sitting in isolation, simply staring at the waves crashing against each other. However, even in those moments of stillness and silence, Taehyun stays to watch. 

Because humans truly are strange. 

But beautiful. 

  
  
  
  
  
  
  


On one of Taehyun’s usual trips back to the boulder he hides behind to observe the land, a friend abruptly blocks his path midway. 

With crossed arms and raised brows, Soobin questions him, “Where do you think you’re going?”

Taehyun resists the urge to roll his eyes. “I’m swimming upwards hyung, where else would I be going?”

“Hey don’t get sarcastic with me, I’m just concerned about you. I’ve been seeing you way too frequently going up there, what if someone sees you and then suddenly you never come back down here?”

“No one will, I’m always careful,” Taehyun understands that Soobin’s nagging is a result of his worry, so he gives the older what he hopes is a reassuring squeeze on the shoulder. “I’ll come back every time.” 

“Just- Don’t be too obsessed with it!” Soobin yells as the other drifted away. 

Upon arriving at his usual spot a few feet away from the shore, Taehyun’s sharp eyes catch an object gleaming from the distance. He surreptitiously moves closer, too intrigued to mind the voice at the back of his head warning him that someone might see. 

When his fingers first come in contact with the sand, Taehyun immediately pulls his hand back as if the grains burned him, startled by the sand’s dryness. It’s new, but not frightening. The siren soon finds himself brave enough to reach out again and fully grasp the object that lured him in the first place. 

In his hands, it’s golden and circular with a chain also made of the same, heavy gold attached to it. Taehyun plays and fiddles with it, trailing his eyes over every part of it in an attempt to identify or at least have an idea of what it is. 

“Oh my god, I knew it.” 

At the sudden intrusion of someone’s voice, Taehyun’s heart drops, fear squeezing the very center of his chest. The surface had welcomed him more than once with wonders he’ll never find under the sea, but now he has overstayed his visit—and he’s not about to wait and see what the consequences are. 

Taehyun drops the object and pushes himself using his arms back to the less shallow part of the water, ready to swim away. 

“Wait!” He hears the human call, but ignores it. If he stops now, who knows where he’ll end up? 

“Stop! Please! You like it when I dance, right?”

This makes Taehyun turn around, but only after deeming himself far enough for the human to be unable to catch him. 

Dance. He’s never heard that word before. It piques his curiosity, a feeling Taehyun has always been unable to resist. Well, the boy has already seen him, might as well ask what it is. He can simply dive back down if he feels that he’s in danger anyway. “Dance? What is that?”

“It’s when uh… It’s when I move my arms and legs? I sway them to a beat!”

Taehyun tilts his head and squints his eyes, now more carefully taking in the appearance of the human. Only until then does he realize it’s the same person he’s been watching. “...how did you know?”

“What?”

“How did you know I like watching you dance?”

“I don’t know, I just,” The boy scratches the back of his head, a shy smile slowly making its way to his face. “I noticed the waves calm down when I do.”

The statement manifests heat across Taehyun’s cheeks. As one of the sons of Yongwang, the god of the sea, he’s aware that his emotions can at times have an effect over the waves. 

Hence he’s also aware that he has the ability to calm the waters in his moments of complete contentment. 

Had he become fond of the human’s  _ dance _ that much? 

He chases the thought away, it’s too embarrassing to ponder on further. “Moving on! I’m still leaving, even if I do like… observing you. How can I be sure you won’t hurt me? Or call other people to help you capture me?” 

“As I’ve told you, I’ve already known for a while that you’ve been regularly visting the shore. So,” The stranger replies with conviction, “If I did want to hurt you, wouldn’t I already have?” 

This silences Taehyun. There  _ is _ truth to the query, and the reply came no later than a second too, it couldn’t have been a lie if the boy didn’t even need time to think about it right? 

Sensing the other’s remaining doubt, the human proposes, “Alright, you don’t even have to come near. Keep staying behind your boulder, but can I at least know your name? I’ll say mine first so you can trust me. My name is Huening Kai.” 

“A name won’t get me to trust you,” The siren retorts, but nonetheless complies.“Mine is Taehyun.” 

At that, the corners of the stranger’s—Huening Kai’s—mouth quirk upwards, before stretching to form a bright beam. “Okay, nice to meet you.” 

One is standing still at the sand, while the other is submerged in the saltwater. 

Taehyun wonders how even at this distance, a smile can send his heart into a mess of palpitations and skipped beats. 

  
  
  
  


On the next visit, Huening Kai appears excited. When Taehyun arrives at his boulder, the former holds his arm up to show off something in his hand. It’s the same golden, circular object he was trying to identify previously. 

“You didn’t seem to know what this is when we met,” Kai starts loudly to make sure he’s heard. “This is called a pocket watch, it’s mine but I can just get a new one. Here!” He throws it to the other’s direction. 

Due to the large proximity between them, the watch fails to reach Taehyun, he swims down however to retrieve it. 

“If you open it by pressing the little button at the top, it shows numbers that help you tell the time!” Kai explains after Taehyun rose back to the surface. “I’m not sure how time works under the sea though.” 

“At least where I am, we don’t live deep enough for the light not to reach us, so we depend on it to tell time.” The other responds in a daze, still preoccupied with the pocket watch. 

“The light? You mean the sun?”

The sun. So that’s what it’s called. 

The new knowledge gives Taehyun a hurl of new questions to ponder on. Just how many more things do humans have a name for? Do they have a name for everything?

If they do, then Taehyun wants to ask Huening Kai if he has a name for the adrenaline he feels each time he swims towards the land, for the spark that buzzes within his system whenever he watches Kai dance. 

He wants to ask Kai if there’s a name for the unfamiliar, but not unwelcome ache to be closer. 

However, instead of doing so, Taehyun settles on asking the human about other inventions their kind have made, believing that the sensations that have been increasingly consuming him with each visit are most likely too odd, even for people, to be named. 

  
  
  
  
  
  


“So this is a hairbrush, we use it to help tame our hair when it becomes unruly. And then this is a mirror, we use it to see ourselves—look! Then this one is called-“

“Huening Kai.” Taehyun cuts the said boy off mid-explanation. After the siren’s initial fascination with the pocket watch, Kai began to bring various objects to introduce, which the former very much appreciated. 

Taehyun also learned to be more at ease around the boy. Kai had been nothing but nice and understanding towards him, never pushing the other to come closer and simply moves on to the next object he wants to show. Hence Taehyun later becomes comfortable with sitting next to him rather than talking from afar. 

However, he realizes just now a query he should have asked from the start. “I forgot to ask.”

“Hm?”

“Why weren’t you afraid when you first saw me?”

Kai pauses, as if contemplating on his answer. He puts down the compass he was about to flaunt before laying on his back, not caring about the damp sand that might cling onto his pristine blouse. “You can say I’ve been aware that mermaids exist.”

Taehyun rolls his eyes, he knows about the other childish name men call his kind. “We’re  _ sirens _ . And what do you mean you’ve known?” 

“When I was a child, my mother used to tell me stories about a creature by the sea she met. She said he was the most beautiful being she’s ever seen, he had the loveliest voice too apparently. There was never a day that she didn’t come see him.” 

“Oh? Why?”

“She fell in love.”

“...oh.” 

“Yeah, oh,” Kai releases a breathless chuckle. “It’s weird right? A human falling in love with a mer—sorry,  _ siren _ .” He corrects himself when Taehyun sends him a glare. 

“The siren didn’t feel the same way though, so she had to nurse a broken heart. But anyway, I honestly couldn’t believe it at first. Why would she fall for someone who was basically a completely different kind from her? I used to always ask myself that but I could never think of an answer, I could never understand.” 

Huening Kai fixates his gaze onto Taehyun. The playful expression he wore before now replaced by one that’s more meaningful. The wind softly blows upon them like a whisper, but Kai’s raven curls fail to hide the indecipherable glint dancing in his eyes. 

And for the first time, Taehyun discovers how it feels to drown. 

“But I think now I do.” 

  
  
  
  
  
  
  
  


Taehyun stares in admiration at the ornaments surrounding him. Each one that Huening Kai gave him, he kept safely in a hidden cave he found, ensuring that no other siren will find them. He’s not worried at all about the possibility of someone stealing, rather he’s more anxious about the likelihood of his father catching him red-handed. 

The god will definitely destroy everything, considering his deep hatred for the surface. However, what distresses Taehyun the most is knowing that if his father indeed does find out what he’s been hiding, he’ll make it certain that Taehyun is unable to swim to land ever again. Perhaps even going to the point of entrapping him alone at the bottom of the sea. 

He’ll never see Huening Kai again. 

Kai. His chest constricts even at the mere thought of the boy. 

The siren isn’t sure of when exactly he began to  _ like _ Huening Kai. Or maybe he should have known the moment he came back to the shore to watch him dance. 

All Taehyun knows is that when he closes his eyes, the image of Kai being kissed by the orange, pink glow of the sky flickers in his mind—and he understands how it feels to yearn for the impossible. 

  
  


“So this is where you’ve been.”

He swivels around in panic to find Soobin with crossed arms and an unimpressed expression registered on his face. “Did you follow me?”

The older ignores the accusation. “You’ve been acting so secretive lately and you’ve been spending more time on the surface too. All these strange objects, where did you even get them?”

“I just.. found them on the shore.” 

“And now you even swim close enough to reach the shore? You used to stay at least a few feet away from it. Tell me, Taehyun.” Soobin moves toward the other siren, giving him no space to escape, giving him no room to lie. “Did you meet a human?” 

With all the false excuses he’s been spilling to conceal his secrets, Taehyun is pushed into a corner with nowhere left to run and nothing left to do but to admit. “I fell for one.” 

He turns away in shame and with a wavering voice, attempts to apologize. “I’m sorry. I didn’t mean to- I just- I’m really sorry.” 

“No  _ I’m _ sorry, Hyun. I’m not mad at you, I’m not telling anyone about this either, okay? Don’t cry.” Soobin pulls Taehyun in for a hug, hoping to convey comfort through the tight grip of his fingers. Small bubbles flow upwards from the latter’s eyes as he continued to shed tears. 

“I didn’t mean to.”

“I know.” 

“I’ve never wanted anything this bad, it hurts. I don’t want to just keep hearing about his day, I want to see it for myself too, right by his side.” 

“...What if I told you there’s a way to do that?” 

Hearing this, Taehyun stiffens and gently releases himself from his friend’s embrace. “What do you mean?”

Soobin bites his lip, looking as if he wants to take it back, but relents with a deep sigh after noticing the younger’s clear desperation. “I recently made a new friend, his name is Beomgyu. He told me once that he fled from another kingdom located deeper in the sea, a bleaker part of it. And now he’s under the care of.. Yeonjun.” 

“Yeonjun? The sea sorcerer Yeonjun? He’s real?” The name is familiar to Taehyun, it’s one that he’s heard of from countless tales. Based on rumors, Yeonjun possesses power that’s inferior only to the god of the sea himself. However, he uses it neither to help nor harm others, unless he’s paid to. 

“Do you know how to get to him?” Perhaps it’s pitiful how much Taehyun is willing to let go of for the sake of spending even a few moments on land with a human, but at this point, he’d rather appear pathetic in the eyes of others than be away from Kai. 

“I think Beomgyu once told me how to get there, in case I ever wanted to visit him. They live together.” 

“Show me the way, please.” 

  
  
  


After passing along sunken boats, ridges, and trenches that Taehyun usually avoids, the pair eventually end up in front of shipwreck in an area barely within the sunlight’s reach. Taehyun is sure it’s still morning, or at the very latest, early afternoon. Yet he can barely see anything outside the rubble of the pirate ship. 

“Beomgyu? It’s Soobin!” The older siren calls out. 

No answer. 

“Beomgyu? You told me to visit whenever! Beomgyu? Are you there? Beom-“

Soobin halts his calls when a figure comes out through the ship’s doorway. But instead of Beomgyu, they’re met with a spine-chilling siren. 

With glowing, ice blue orbs, Yeonjun interrogates them. “Beomgyu is asleep, what do you need from him? Or wait… are you from Halmang’s kingdom? I’m not letting you take Beomgyu away if that’s what you’re here for.” 

“No!” Taehyun interjects, not wanting to aggravate the sorcerer before he’s even made his request. “We’re not here to take away anyone, we came here to ask something from you, actually.” 

The reply appeases Yeonjun, who loosens his clenched fists and dims the intimidating flare in his eyes. “Alright, but before we talk, you have to know that I don’t do anything without something just as important in return.”

“I know.” 

“Come inside then.” 

Both Soobin and Taehyun hesitantly follow the sorcerer as they’re led to the lower portion of the ship, most likely to steer them away from the sleeping Beomgyu. 

“You know,” Yeonjun starts. “The moment I saw you I could already tell what your desire is, and how far you’re willing to go. Are you sure it’s what you want?” 

He looks at Taehyun like he’s persuading the latter to think about his next decision more deeply, but there’s no need for that, really. It’s not as complicated as the sorcerer believes it to be. 

The answer to the question relies on the simple, indisputable fact that Taehyun longs to be with Huening Kai. He aches for that moment, more than anything else. 

“Yes, I’m sure.” 

Yeonjun’s eyebrows furrow and opens his mouth to disapprove, he quickly closes it however, realizing that he shouldn’t concern himself with the other’s business. “Okay, I can give you human legs. But what do I get in return?” 

Taehyun dwells on the different aspects of himself, he’s willing to give up just about anything, but what would be enough to satisfy the sea’s only sorcerer? 

“My voice.”

“Your voice?”

“Think about it,” Taehyun tries his best to sound convincing, this could be his last, if not only chance to be with Kai. “Nothing else can be more important to a siren than their voice.” 

Clarity falls upon Yeonjun’s face. He’s satisfied. “Very well, legs in exchange for your voice. But listen, I’m not cruel enough to permanently take away your voice and your fins. If at any point you wish to return to being a siren, then simply dip your feet into the sea from where you rose from.” 

“However,” His tone shifts into one of warning. “Once you do that, you’ll have both your fins and your voice back, but you can never turn human again. Understand?” 

Following a single nod from Taehyun, Yeonjun places a luminescent hand on his forehead. 

  
  
  


The last thing the former sights is sadness painted on Soobin’s face, regretful to see his best friend go, before he feels himself being shaken awake. 

“Taehyun? Wake up!” 

The said boy snaps straight up from the sand and begins coughing out saltwater. His throat burns, as if the sea urchins he usually found within coral reefs were instead lodged within his neck. 

“Is it really you? Are you okay?” 

Taehyun turns to the voice and finds an astonished Huening Kai. Yes, it’s me. He tries to say, but no sound is heard. 

Right. He doesn’t have a voice anymore, he exchanged it for—

_ Legs! _ Taehyun frantically gestures to the lower part of his body, which now bore human legs and feet instead of his large fin. 

“I know! You’re.. human now. But how?” Kai asks, then turns to the other when he gets no response. 

Taehyun repeatedly points at his throat with his mouth open, before gesturing a cross using his arms. He wants to explain every detail of the event to the boy, wants to tell him that he’s here because of him, but he’s rendered unable to do either. 

“You can’t speak anymore?” 

Taehyun nods, relieved that the other understood. 

“Oh Taehyun, what did you do?” Huening Kai cups the mute boy’s left cheek, a simple touch which the latter immediately melts into. 

He’s used to the coldness of the sea, to the skins and scales of other sea creatures that felt just as icy. Taehyun lets his eyes flutter shut as he savors the warmth. 

He would surrender everything and more all over again if it meant spending a moment longer like this. 

Eventually, Kai’s initial confusion passes and he composes himself to carry Taehyun, who kept stumbling before he could even stand, to a castle. 

A castle, a marvelous one. 

“I never told you I’m uh, I’m a prince here on land.” Huening Kai explains after noticing Taehyun’s eyes widen at the luxurious interior of the palace and the servants who all bow at the sight of them. “It’s why you never see anyone on the shore besides me, my family owns that beach and anyone can use it, but no one likes going except for me.” 

“Oh I realized, your timing is perfect actually!” Kai continues enthusiastically. “The ball is tonight. You remember the dance I’ve been showing you? I’ve been practicing to perform it later!” 

Taehyun recalls it perfectly, he’s watched the taller so many times he’s sure he’ll know what specific movement Kai is doing even with his eyes closed. 

As he gets scrubbed clean and dressed by various servants, Taehyun delights himself with scenarios of what would possibly greet him at the formal ball. He’ll be surrounded by so many other people for the first time. He’ll be able to dine with them and learn much more about how they live. Perhaps with Kai’s guidance, he might even be able to dance too. 

Daydreams and expectations fill him with excitement. 

None preparing him for how devastating reality is.

Before leaving to tend to guests and prepare for his performance, Huening Kai left Taehyun to sit by one of the tables, since the latter still wasn’t used to his legs. 

Everything flowed smoothly in the beginning and Taehyun was content with being seated alone, quietly observing his grand surroundings. Everything had been fine. 

Until he noticed the mocking glances and snickers sent his way. 

It started with brief looks, which later escalated into direct insults from elites who were shameless enough to head Taehyun’s way and laugh at him, calling him malicious names. 

“He smells like seaweed and raw fish, how did this mute stranger manage to sneek into this party?” Taehyun heard a dutchess say to another, not bothering to lower her voice. 

His breaking point, however, was when he didn’t even get to see Kai dance. All the other guests were blocking his line of vision and he could only stand for a few minutes before he fell on his legs again. 

When his night ended with a damp pillow, Taehyun convinced himself that things would get better, it’s only his first day away fron sea after all. 

But they didn’t. 

After properly learning how to walk, Taehyun was only greeted by loneliness within the empty castle. He understood that although they did spend much more time together now, Huening Kai can’t be with him all the time since the prince had meetings and lessons to attend. 

None of the servants ever gave him a warm welcome either, most of them ignored him while some treated him coldly out of jealousy. Taehyun couldn’t blame them—he’s a stranger, an intruder. Someone who doesn’t belong. 

The feeling of alienation later morphs into guilt. Why is he longing to go home when Huening Kai, the only thing he’s ever wanted, is right here? Shouldn’t that be enough? 

“Do you miss the sea?” Kai asks him one night, three weeks after losing his fins, noticing his dark circles and miserable state.

Taehyun wanted to deny, wanted to cling onto the other boy and assure him that he’s happy as long as he’s with him. 

But the tears that he failed to prevent from falling answered the question for him. 

“You can go back anytime, even right now, I’ll take you.” 

Taehyun frantically shakes his head in refusal despite Kai already knowing how much he does want to go back. He grasps both of the latter’s hands and pulls them towards his chest, right where his beating heart is. 

_ You’re here with me, and that’s enough. _

Kai stares at the crying male in silence. His gaze resembles the one from the shore, when they talked about his mother and Taehyun didn’t understand why he swam back down with an even stronger desire to be with the human. 

“Taehyun, look at me.” 

It takes him a few more minutes of crying, but he eventually complies. 

Huening Kai smiles at him and places his own forehead against his. “Taehyun, you can take it wherever you want. Whether in sea or on land, you will always have my heart with you.” 

The prince kisses each tear away. “I know that this world isn’t too kind, which is why I keep going back to you. You make me realize that there are some things in this world that are still worth forgiving.” 

“So please know that going back to the sea doesn’t mean losing me. Now let me ask you again, do you want me to take you back?”

Taehyun had never been more grateful than this moment. He has Huening Kai who is always so kind, Huening Kai who he never had to hide any part of himself from. 

Huening Kai who loves him back. 

_ Okay.  _

Taehyun nods. 

  
  
  


That same night, Kai carries the other back to the same beach where they met. He gapes in awe as he watched the  _ siren’s _ human legs shift back to one large fin.

They separate that night with a chaste kiss, their first one. It left both of them wanting more, but only contentment fills their parting. 

Taehyun knows it’ll be difficult with the distance and the fact that he’s yet to tell his father. 

But it’s okay. 

Because Taehyun is more than just a siren that wandered too far and Huening Kai is more than just a prince that was at the right place at the right time. 

Together, they’re a promise that formed from tender whispers and hidden laughter within the sphere’s boundaries—where land and sea meet on the shoreline. 

**Author's Note:**

> me trying to fit together scenes like a pack of sardines 'cause it has to be in the 4k range
> 
> if you liked this fic, please consider leaving a kudos and a comment ! thank you :]
> 
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